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Definition

Proxy data (GHG accounting)

Proxy data fills a defined GHG accounting gap with information from a similar activity, site, period, or supplier, while documenting the substitution, reason, calculation, and limitation for review.

What is proxy data in GHG accounting?

Proxy data uses one known activity to estimate another activity with missing data. In its Scope 3 measurement framework, AASB S2 paragraph B49 classifies that substitution as secondary data, even if the source record is primary for its original activity.

Why does proxy data matter to you?

A customer or reviewer may ask which inventory lines are estimated. For each proxy, keep the missing period, site or supplier, the substitute chosen, the reason for the choice, the calculation, the share of emissions affected, and the owner responsible for replacement.

How should you choose proxy data?

Define the missing activity and unit first. Compare candidates against the same technology, country, reporting period, scale, and what the source covers. For Scope 3 secondary data, AASB S2 paragraphs B50-B52 require you to prioritise matches for technology, jurisdiction, and reporting period. Check scale and coverage separately. Apply any scaling separately, label the result as estimated, and retain both the source record and calculation file.

What mistakes should you avoid?

  • Using another country's electricity factor without recording the geographic mismatch.
  • Copying one supplier's result to another supplier with different products or processes.
  • Hiding proxy use inside a calculated total or calling the estimate primary data.
  • Leaving a material proxy unchanged after better data becomes available.

Is proxy data the same as an emission factor?

No. An emission factor converts activity into emissions. Either the activity value, the factor, or both can be proxies, so label each substituted input separately.

When should you replace proxy data?

Replace it when a more representative meter record, invoice, supplier figure, or factor becomes available, prioritising high-emission lines and poor matches first. Recalculate the affected total and preserve the previous version.

What should you send when a customer asks about a proxy?

Send the inventory line, missing-data note, source document, comparison against technology, country and year, scaling formula, percentage of the category affected, limitation, reviewer name, and replacement date.

Example

Suppose a renewable-energy EPC contractor in the Netherlands lacks 2025 fuel records for one of four similar installation vans. The other three vans used 460, 500, and 540 litres during the same quarter. Their average is (460 + 500 + 540) / 3 = 500 litres, which the contractor uses as the missing van's proxy.

The estimated total for all four vans is 460 + 500 + 540 + 500 = 2,000 litres. The proxy therefore covers 500 / 2,000 = 25% of that quarter's recorded and estimated van fuel. The contractor records the matching vehicle class, work pattern, country, period, source invoices, calculation, and the fact that 25% of the total is estimated. It replaces the 500-litre estimate when the missing invoice arrives.

Where it comes up

AASB S2 proxy data used to estimate another value-chain activityAASB S2 paragraph B49AASB S2 technology, jurisdiction and reporting-period tests for secondary dataAASB S2 paragraphs B50-B52

Related terms

Primary vs secondary GHG data

Primary GHG data records a specific site, product, activity, or supplier, while secondary GHG data estimates that activity with external averages, databases, financial factors, or other proxies.

Emission factor

An emission factor converts a measured activity, such as kilowatt-hours of electricity or litres of fuel, into greenhouse gas emissions by stating the emissions released per unit of that activity.

GHG inventory

A GHG inventory is a dated record that fixes an organisation's boundary, lists its emissions sources and calculations, separates Scope 1, Scope 2 and Scope 3 totals, and documents methods, exclusions and supporting files.

Scope 3 Emissions

Scope 3 emissions are the indirect greenhouse gas emissions from goods, services, transport, product use, investments, and other upstream and downstream activities outside your company's Scope 1 and Scope 2 boundary.

Sources

  • GHG Protocol

    Chapter 7 definition of proxy data, section 7.5 gap-filling method, scaling and data-quality tests

    2026-08-20

  • Australian Accounting Standards Board

    Paragraphs B49-B52 on proxy data as secondary data and matching technology, jurisdiction and reporting period

    2026-08-20

Last verified 2026-08-20

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Proxy data (GHG accounting) Definition | Keslio